import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;



/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: 19182
 * Date: 2025-09-22
 * Time: 14:34
 */
public class UdpEchoServer {
    private DatagramSocket socket = null;
    public UdpEchoServer(int port) throws SocketException {
        socket = new DatagramSocket(port);
    }
    public void start() throws IOException {
        System.out.println("服务器启动:");
        while(true){

            //1.解析并读取请求数据包Q
            DatagramPacket requestPacket = new DatagramPacket(new byte[4096], 4096);
            socket.receive(requestPacket);
            String request = new String(requestPacket.getData(), 0, requestPacket.getLength());
            //2.根据请求，计算响应
            String response = process(request);
            //3.构造响应数据包
            DatagramPacket responsePackeet = new DatagramPacket(response.getBytes(), response.getBytes().length
            , requestPacket.getSocketAddress());
            //4.发送响应数据包
            socket.send(responsePackeet);
            //5.打印日志
            System.out.printf("[%s:%d] req:%s, resp:%s", requestPacket.getAddress().toString()
                    , requestPacket.getPort(), request, response);
        }
    }

    private String process(String request) {
        return  request;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer udpEchoServer = new UdpEchoServer(9090);
        udpEchoServer.start();
    }
}
